We are studying the effects of vitamin D deficiency upon growth and muscle protein turnover in the rat. We hope to determine the cause of the decreased growth seen in vitamin D deficiency by the use of both in vivo studies and in vitro experiments in a perfused muscle system. We plan to perform perfusion studies to determine separate rates of synthesis and degradation in vitamin D deficient as well as vitamin D replete animals. We will also examine muscle levels of RNA, DNA, high energy phosphate compounds, and the ratio of 40 plus 60 S ribosomal subunits to total RNA. We plan to determine whether the transcription or translation in protein synthesis are effected by vitamin D deficiency. The use of vitamin D metabolites will be assessed to determine the metabolites responsible for the increased anabolism seen after vitamin supplementation.